A modern jet aircraft typically includes several hundred multi-wire harnesses for electrically connecting various aircraft subsystems. Such harnesses can conveniently be broken down into two types, integration harnesses and ships harnesses. Integration harnesses are comparatively short but include a large number of individual wires and typically a large number of branch points. Ships harnesses typically comprise a small numer of long wires.
Under current technology, different manufacturing methods are used for integration and ships harnesses. The first step in forming an integration harness is to run raw wire through a wire coding machine, such as the wire coding machine available from Conrac, or an equivalent device. The Conrac machine operates under the control of a computer that includes a data base specifying the lengths and code numbers of the individual wires required for a set of harnesses. The Conrac machine provides instructions to the operator concerning the type of raw wire to be mounted on an input spool, and then unreels, codes and places pinch marks on the wire as the wire is transferred from the input spool onto an output spool. Coding is accomplished by a hot stamp process in which identifying code symbols (e.g., numbers) are printed on the wire insulation. The pinch mark mechanism of the Conrac machine requires the wire to be stationary when the pinch mark is applied. The Conrac machine can also cut the wire rather than pinch it. The cutting mechanism also requires the wire to be stationary when the cut is made.
The wire spools coded and pinched by the Conrac machine may be further processed using a computer aided, hand-forming (CAHF) system. In a CAHF system, a formboard is created for each cable, the formboard comprising a planar baseboard, a drawing attached to the baseboard with imprinted instructions and diagrams relating to wire routing, and pegs projecting above the baseboard around which wire can be routed or to which wire can be tied off. In response to instructions displayed on a portable computer monitor, a CAHF operator unreels coded and pinched wires from the spools produced by the Conrac machine, and winds such wires on the formboard pegs, using the codes and pinch marks to verify correct placement. The continuous wire is cut inboard of the pinch marks at the connector cut line indicated on the drawing attached to the baseboard, such that all pinch marks are removed from the completed wire harness.
Under present technology, ships harnesses are typically created by a conventional lay-down process. In such a process, a Conrac machine is first used to code and cut individual wires. For efficiency, a Conrac operator loads a given wire type on the input spool of the Conrac machine, and then codes and cuts all wire segments that will be required from that reel for a given set of harnesses, the set of harnesses typically corresponding to one day's work. After each wire segment has been coded and cut, the operator manually coils the cut wire and places it in an output group corresponding to a given harness and harness subassembly. When the Conrac operator has collected a complete set of wires for a given harness, these wires are then routed to a follow on stage that applies a connector to one end of the harness. The harness with the connector on one end is then laid out on a conventional formboard, and then processed through a station that applies a connector to the other end of the harness.
In recent years, ink jet machines have become available that are capable of applying codes to wire while the wire is moving rapidly through the machine, at speeds up to 350 feet per minute. Ink jet machines therefore make possible a high speed, spool-to-spool, wire coding process in which wire is continuously unwound from an input spool, coded in the ink jet machine, and rewound onto an output spool. The ink jet machine identifies the beginning and ending of each wire segment with a block mark that comprises a pair of closely spaced bars. The block mark indicates the boundary between adjacent wire segments, and the small space between the bars for a block mark is the intended cut line. Unless multiples of the same wire are being coded, the code applied to each wire segment changes with each block mark.